Acrisio Pires and alumna Emily Coppess (BA, 2011; now at U. of Chicago) gave the invited paper 'The residue of syntactic change: Partial pro-drop in Old English?', at the Workshop on Diachronic Syntax, held on June 29-30, 2013, at the LSA Linguistic Institute, in Ann Arbor.
Old English had null subjects, but the frequency of referential null subjects was very low, and they mainly occurred in restricted
syntactic domains. This paper evaluates this apparent residual nature of null subjects in view of formal approaches to partial pro-drop, and argues that in the late stages of Old English its grammar no longer had referential (pro) null subjects, although it still allowed expletive null subjects.